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The Lockheed Martin F-35 Lightning II is a family of single-seat, single-engine, fifth generation multirole fighters under development to perform ground attack, reconnaissance, and air defense missions with stealth capability.

The F-35 has three main models; the F-35A is a conventional takeoff and landing variant, the F-35B is a short take off and vertical-landing variant, and the F-35C is a carrier-based variant.

The F-35 is descended from the X-35, the product of the Joint Strike Fighter (JSF) program. JSF development is being principally funded by the United States, with the United Kingdom and other partner governments providing additional funding.

The partner nations are either NATO members or close U.S. allies. It is being designed and built by an aerospace industry team led by Lockheed Martin.
The F-35 took its first flight on 15 December 2.006.

The United States intends to buy a total of 2,443 aircraft to provide the bulk of its tactical airpower for the US Air Force, Marine Corps and Navy over the coming decades.

The United Kingdom, Australia, Italy, Canada, Netherlands, Norway, Turkey, Israel, and Japan all will equip their air and/or naval forces with the F-35.
However, the Japanese have warned that they may halt their purchase if the unit costs increase.
Similarly, Canada indicated they are not fully committed to purchasing the aircraft.

The United States is projected to spend an estimated US$323 billion for development and procurement on the F-35 program, making it the most expensive defense program ever.
Its total lifecycle cost is estimated to be US$1 trillion over its 50-year life.

Development

The JSF program was designed to replace the United States military F-16, A-10, F/A-18 (excluding newer E/F "Super Hornet" variants) and AV-8B tactical fighter aircraft.

To keep development, production, and operating costs down, a common design was planned in three variants that share 80 percent of their parts :
F-35A, conventional take off and landing (CTOL) variant.
F-35B, short-take off and vertical-landing (STOVL) variant.
F-35C, carrier-based CATOBAR (CV) variant.

An F-35 wind tunnel testing model in the Arnold Engineering Development Center's 16-foot transonic wind tunnel.

George Standridge of Lockheed Martin has said that the F-35 will be four times more effective than legacy fighters in air-to-air combat, eight times more effective than legacy fighters in air-to-ground combat, and three times more effective than legacy fighters in reconnaissance and suppression of air defenses  while having better range and requiring less logistics support and having around the same procurement costs (if development costs are ignored) as legacy fighters.

Further, the design goals call for the F-35 to be the premier strike aircraft through 2040 and be second only to the F-22 Raptor in air superiority.
While the actual JSF development contract was signed on 16 November 1.996, the contract for System 
Development and Demonstration (SDD) was awarded on 26 October 2.001 to Lockheed Martin, whose X-
35 beat the Boeing X-32.

Although both aircraft met or exceeded requirements, the X-35 design was considered to have less risk and more growth potential.
The designation of the new fighter as "F-35" is out-of-sequence with standard DoD aircraft numbering, by which it should have been "F-24".
It came as a surprise even to Lockheed, which had been referring to the aircraft in-house by this expected designation.

Design phase

Based on wind tunnel testing, Lockheed Martin slightly enlarged its X-35 design into the F-35. The forward fuselage is 5 inches (130 mm) longer to make room for avionics.
Correspondingly, the horizontal stabilators were moved 2 inches (51 mm) rearward to retain balance and control.

The top surface of the fuselage was raised by 1 inch (25 mm) along the center line. Also, it was decided to increase the size of the F-35B STOVL variant's weapons bay to be common with the other two variants.

Manufacturing of parts for the first F-35 prototype airframe began in November 2.003.

The F-35B STOVL variant was in danger of missing performance requirements in 2.004 because it weighed too much; reportedly, by 2,200 lb (1,000 kg) or 8 percent.
In response, Lockheed Martin added engine thrust and thinned airframe members; reduced the size of the common weapons bay and vertical stabilizers; re-routed some thrust from the roll-post outlets to the main nozzle; and redesigned the wing-mate joint, portions of the electrical system, and the portion of the aircraft immediately behind the cockpit.

Many of the changes were applied to all three variants to maintain high levels of commonality.
By September 2.004, the weight reduction effort had reduced the aircraft's design weight by 2,700 pounds (1,200 kg).
On 7 July 2.006, the US Air Force officially announced the name of the F-35: Lightning II, in honor of Lockheed's World War II-era twin-prop Lockheed P-38 Lightning and the Cold War-era jet, the English 

Electric Lightning.

English Electric Company's aircraft division was a predecessor of F-35 partner BAE Systems. Lightning II was also an early company name for its fighter that was later named the F-22 Raptor.
On 19 December 2.008, Lockheed Martin rolled out the first weight-optimized F-35A (designated AF-1).
It is the first F-35 to be produced at a full-rate production speed and is structurally identical to the production F-35As that will be delivered starting in 2.010.

Lockheed Martin Aeronautics is the prime contractor and performs aircraft final assembly, overall system integration, mission system, and provides forward fuselage, wings and flight controls system.
Northrop Grumman provides Active Electronically Scanned Array (AESA) radar, electro-optical Distributed Aperture System (DAS), Communications, Navigation, Identification (CNI), center fuselage, weapons bay, and arrestor gear.

BAE Systems provides aft fuselage and empennages, horizontal and vertical tails, crew life support and escape systems, Electronic warfare systems, fuel system, and Flight Control Software (FCS1).
Alenia will perform final assembly for Italy and, according to an Alenia executive, assembly of all European aircraft with the exception of Turkey and the United Kingdom.

The F-35 program has seen a great deal of investment in automated production facilities.
For example, Handling Specialty produced the wing assembly platforms for Lockheed Martin.
In November 2.009, Jon Schreiber, head of F-35 international affairs program for the Pentagon, said that the U.S. will not share the software code for the F-35 with its allies.

As of 5 January 2.009, six F-35s were complete, including AF-1 and AG-1, and 17 were in production.
"Thirteen of the 17 in production are pre-production test aircraft, and all of those will be finished in 2.009," said John R. Kent, acting manager of F-35 Lightning II Communications at Lockheed Martin Aeronautics Company. "

The other four are the first production-model planes, and the first of those will be delivered in 2.010 to the U.S. Air Force, and will go to Eglin Air Force Base."
On 6 April 2.009, US Secretary of Defense Robert Gates proposed speeding up production for the US to buy 2,443 F-35s.

In August 2.010, Lockheed Martin announced delays in resolving a "wing-at-mate overlap" production problem, which would slow initial production.

In October 2.011 two F-35B VTOL aircraft conducted three weeks of initial sea trials aboard USS Wasp (LHD-1), logging more than 28 hours of flight time including 72 short take-offs and 72 vertical landings.

Program cost increases and further delays

In 2.006, the GAO warned that excessive concurrency in F-35 production and testing might result in expensive refits for several hundred aircraft planned to be produced before completion of tests.
In November 2.010, the GAO found that "Managing an extensive, still-maturing global network of suppliers adds another layer of complexity to producing aircraft efficiently and on-time" and that "However, due to the extensive amount of testing still to be completed, the program could be required to make alterations to its production processes, changes to its supplier base, and costly retrofits to produced and fielded aircraft, if problems are discovered."

The United States Air Force (USAF) budget data in 2.010, along with other sources, projects the F-35 to have a flyaway cost from US$89 million to US$200 million over the planned production of F-35s.
In February 2.011, the Pentagon put a price of $207.6 million for each of the 32 aircraft to be acquired in FY2012, rising to $304.15 million ($9,732.8/32) if its share of RDT&E spending is included.
In 2.011, program head Vice Adm. David Venlet confirmed that the concurrency built into the program "was a miscalculation".

This was during a contract dispute where the Pentagon insisted that Lockheed Martin help cover the costs of applying fixes found during testing to aircraft already produced.

Lockheed Martin objected that the cost sharing posed an uninsurable unbounded risk that the company could not cover, and later responded that the "concurrency costs for F-35 continue to reduce".
However the Senate Armed Services Committee strongly backed the Pentagon position.
In December 2.011 Lockheed Martin agreed to a cost sharing agreement.

The Aerospace Industries Association trade group warned that such changes would force them to change their behavior and anticipate cost overruns in their future contract bids.
As of 2.012, problems found in flight testing are expected to continue to lead to elevated levels of engineering changes (to be made to newly produced aircraft and retrofitted onto previously produced aircraft) through 2.019.

In 2.012, Schwartz decried the "foolishness" of reliance on computer models to settle the final design of the aircraft before flight testing found the issues that needed redesign.
On 21 April 2.009, media reports, citing Pentagon sources, said that during 2.007 and 2.008, computer spies had managed to copy and siphon off several terabytes of data related to the F-35's design and electronics systems, potentially enabling the development of defense systems against the aircraft.

However, Lockheed Martin has rejected suggestions that the project has been compromised, saying that it "does not believe any classified information had been stolen".

However other sources have suggested that the incident caused a redesign of the aircraft's hardware and software to be more resistant to cyber attack.
BAE Systems was reported to be the target of the cyber espionage that may have stolen secrets related to the F-35.

On 9 November 2.009, Ashton Carter, under-secretary of defense for acquisition, technology and logistics, acknowledged that the Pentagon "joint estimate team" (JET) had found possible future cost and schedule overruns in the project and that he would be holding meetings to attempt to avoid these.

On 1 February 2.010, Gates removed the JSF Program Manager, U.S. Marine Corps Major General David Heinz, and withheld $614 million in payments to Lockheed Martin because of program costs and delays.

On 11 March 2.010, a report from the Government Accountability Office to United States Senate Committee on Armed Services projected the overall unit cost of an F-35A to be $112M in today's money.

In 2.010, Pentagon officials disclosed that the F-35 program has exceeded its original cost estimates by more than 50 percent.

An internal Pentagon report critical of the JSF project states that "affordability is no longer embraced as a core pillar".
On 24 March, Gates termed the recent cost overruns and delays as "unacceptable" in a testimony before the U.S. Congress.

He characterized previous cost and schedule estimates for the project as "overly rosy". However, Gates insisted the F-35 would become "the backbone of U.S. air combat for the next generation" and informed the Congress that he had expanded the development period by an additional 13 months and budgeted $3 billion more for the testing program while slowing down production.

Lockheed Martin expects to reduce government cost estimates by 20%.

In November 2.010 as part of a cost-cutting measure, the co-chairs of the National Commission on Fiscal Responsibility and Reform suggested canceling procurement of the F-35B and halving orders of F-35As and F-35Cs.
At the same time Air Force Magazine reported that "Pentagon officials" are considering canceling the F-35B because its short range means that the bases or ships it operates from will be within range of hostile tactical ballistic missiles.

However Lockheed Martin consultant Loren B. Thompson said that this rumor is merely a result of the usual tensions between the US Navy and Marine Corps, and there is no alternative to the F-35B as an AV-8B replacement.

He also confirmed that there would be further delays and cost increases in the development process because of technical problems with the aircraft and software, but blamed most of the delays and extra costs on redundant flight tests.
The Center for Defense Information estimated that the program would be restructured with an additional year of delay and $5 billion in additional costs.
On 5 November 2.010, the Block 1 software flew for the first time on BF-4 which included information fusion and initial weapons-release capability.

As of the end of 2.010, only 15% of the software remains to be written, but this includes the most difficult sections such as data fusion.
But in 2.011 it was revealed that only 50% of the eight million lines of code had actually been written and that it would take another six years and 110 additional software engineers in order to complete the software for this new schedule.

In January 2.011 Defense Secretary Robert Gates expressed the Pentagon's frustration with the skyrocketing costs of the F-35 program when he said "The culture of endless money that has taken hold must be replaced by a culture of restraint."

Focusing his attention on the troubled VTOL F-35B Gates ordered "a two-year probation", saying it "should be canceled" if corrections are unsuccessful.[74] However, Gates has stated his support for the program.

Some private analysts, such as Richard Aboulafia, of the Teal Group state that the whole F-35 program is becoming a money pit.

However, on 20 January 2.012 Gates' successor, Leon Panetta, lifted the F-35B's probation, stating "The STOVL variant has made I believe and all of us believe sufficient progress."
Former Pentagon manager Paul G. Kaminski has said that the lack of a complete test plan has added five years to the JSF program.
As of February 2.011, the main flaws with the aircraft are engine "screech", transonic wing roll-off and display flaws in the helmet mounted display.

The current schedule has the delivery of basic combat capability aircraft in late 2015, followed by full capability block three software in late 2.016.
The $56.4 billion development project for the aircraft should be completed in 2.018 when the block five configuration is expected to be delivered, several years late and considerably over budget.

Delays in the F-35 program may lead to a "fighter gap" where America and other countries will lack sufficient jet fighters to cover their requirements.

Israel may seek to buy second-hand F-15s to cover its gap, while Australia may also seek to buy more American fighters from the USN to cover their own capability gap in the face of F-35 delays.

Initial Operational Capability (IOC) will be determined by software development rather than by hardware production or pilot training.

In May 2.011, the Pentagon's top weapons buyer Ashton Carter said that its new $133 million unit price was not affordable.

In 2.011 The Economist warned that the F-35 was in danger of slipping into a "death spiral" where increasing per aircraft costs would lead to cuts in number of aircraft ordered which would lead to further cost increases and further order cuts.

Later that year four aircraft were cut from the fifth LRIP order to pay for cost overruns.
And in 2.012 a further two aircraft were cut.
And Lockheed acknowledged that the slowing of purchases would increase the costs.
David Van Buren, acquisition chief for the U.S. Air Force, said that Lockheed would need to cut infrastructure to match the reduced market for their aircraft.

Lockheed has said that the slowdown in American orders will free up capacity to meet the urgent short term needs of foreign partners for replacement fighters.

But Air Force Secretary Michael Donley said that there was no more money available for the project and that future price increases would be matched with cuts in the number of aircraft ordered.
Also in 2.011 a Congressional Joint Strike Fighter Caucus was formed by some of the top recipients of Lockheed Martin contributions.

James Jay Carafano of the Heritage Foundation has suggested that it would be cheaper to build additional F-35s with known defective structures and fix these later than it would be to refit legacy aircraft to remain operational until full production of F-35s with full lifespan rated structural components could be built.
The program delays have affected the program's worldwide supply chain, causing Australian Quickstep 

Holdings to struggle for capital, in spite of their 20-year contract with Lockheed Martin.
In order to reduce the estimated $1 trillion cost of the F-35 program over its 50-year lifetime, the USAF is considering reducing Lockheed's role in Contractor Logistics Support for the fighter.
In 2.012, in order to avoid further redesign delays, the US DoD accepted a reduced combat radius for the F-35A and a longer takeoff run for the F-35B.

The F-35B's estimated radius has also decreased 15 percent from initial JSF goal. In a meeting in Sydney in March, the United States pledged to eight partner nations that there would be no more program delays.

Concerns over performance and safety

In 2.006 the F-35 was downgraded from "very low observable" to "low observable", a change former RAAF flight test engineer Peter Goon likened to increasing the radar cross section from a marble to a beach ball.
Andrew Krepinevich has questioned the reliance on "short range" aircraft like the F-35 or F-22 to 'manage' China in a future conflict and has suggested reducing the number of F-35s ordered in favor of a longer range platform like the Next-Generation Bomber, but Michael Wynne, then United States Secretary of the Air Force rejected this plan of action in 2.007.

However in 2.011, the Center for Strategic and Budgetary Assessments (CSBA) pointed to the restructuring of the F-35 program and the return of the bomber project as a sign of their effectiveness, while Rebecca Grant said that the restructuring was a "vote of confidence" in the F-35 and "there is no other stealthy, survivable new fighter program out there".

Lockheed has also said that the F-35 is designed to launch internally carried bombs at supersonic speed and internal missiles at maximum supersonic speed.
In 2.008 it was reported that RAND Corporation conducted simulated war games in which Russian Sukhoi Su-35 fighters defeated the F-35.

As a result of these media reports, then Australian defence minister Joel Fitzgibbon requested a formal briefing from the Australian Department of Defence on the simulation.

This briefing stated that the reports of the simulation were inaccurate and did not actually compare the F-35's flight performance against other aircraft.

The Pentagon and Lockheed Martin added that these simulations did not address air-to-air combat.
A Lockheed Martin press-release points to USAF simulations regarding the F-35's air-to-air performance against potential adversaries described as "4th generation" fighters, in which it claims the F-35 is "400 percent" more effective.

Major General Charles R. Davis, USAF, the F-35 program executive officer, has stated that the "F-35 enjoys a significant Combat Loss Exchange Ratio advantage over the current and future air-to-air threats, to include Sukhois".

The nature of the simulations, and the terms upon which the "400 percent" figure have been derived remains unclear. Regarding the original plan to fit the F-35 with only two air-to-air missiles, Major Richard Koch, chief of USAF Air Combat Command’s advanced air dominance branch is reported to have said that "I wake up in a cold sweat at the thought of the F-35 going in with only two air-dominance weapons."

However the Norwegians have been briefed on a plan to equip the F-35 with six AIM-120D missiles by 2.019.
Former RAND author John Stillion has written of the F-35A's air-to-air combat performance that it “can’t turn, can’t climb, can’t run”, but Lockheed Martin test pilot Jon Beesley has countered that in an air-to-air configuration the F-35 has almost as much thrust as weight and a flight control system that allows it to be fully maneuverable even at a 50-degree angle of attack.

Chen Hu, editor-in-chief of World Military Affairs magazine has said that the F-35 is too costly because it attempts to provide the capabilities needed for all three American services in a common airframe.
Dutch news program NOVA show interviewed US defense specialist Winslow T.
Wheeler and aircraft designer Pierre Sprey who called the F-35 "heavy and sluggish" as well as having a "pitifully small load for all that money", and went on to criticize the value for money of the stealth measures as well as lacking fire safety measures.

His final conclusion was that any air force would be better off maintaining its fleets of F-16s and F/A-18s compared to buying into the F-35 program.
Lockheed spokesman John Kent has said that the missing fire-suppression systems would have offered "very small" improvements to survivability.
In the context of selling F-35s to Israel to match the F-15s that will be sold to Saudi Arabia, a senior U.S. defense official was quoted as saying that the F-35 will be "the most stealthy, sophisticated and lethal tactical fighter in the sky," and added "Quite simply, the F-15 will be no match for the F-35."

After piloting the aircraft, RAF Squadron Leader Steve Long said that, over its existing aircraft, the F-35 will give "the RAF and Navy a quantum leap in airborne capability."
Consultant to Lockheed Martin Loren B. Thompson has said that the "electronic edge F-35 enjoys over every other tactical aircraft in the world may prove to be more important in future missions than maneuverability".

In 2.011, Canadian politicians raised the issue of the safety of the F-35's reliance on a single engine (as opposed to a twin-engine configuration, which provides a backup in case of an engine failure).
Canada had previous experience with a high-accident rate with the single-engine Lockheed CF-104 Starfighter with many accidents related to engine failures.

Defence Minister Peter MacKay, when asked what would happen if the F-35’s single engine fails in the Far North, stated "It won’t".
In November 2.011, a Pentagon study team identified the following 13 areas of concern that remained to be addressed in the F-35:
The Helmet mounted display system does not work properly.
The fuel dump subsystem poses a fire hazard.
The Integrated Power Package is unreliable and difficult to service.

The F-35C's arresting hook does not work.
Classified "survivability issues", which have been speculated to be about stealth.
The wing buffet is worse than previously reported.
The airframe is unlikely to last through the required lifespan.
The flight test program has yet to explore the most challenging areas.
The software development is behind schedule.

The aircraft is in danger of going overweight or, for the F-35B, too heavy for VTOL operations.
There are multiple thermal management problems.
The air conditioner fails to keep the pilot and controls cool enough, the roll posts on the F-35B overheat, and using the afterburner damages the aircraft.
The automated logistics information system is partially developed.

The lightning protection on the F-35 is uncertified, with areas of concern.
In December 2.011 the Pentagon and Lockheed came to an agreement to assure funding and delivery for a fifth order of early F-35 aircraft of yet undefined type in spite of general national austerity measures affecting the program.

Design

The F-35 appears to be a smaller, slightly more conventional, single-engine sibling of the sleeker, twin-engine Lockheed Martin F-22 Raptor, and indeed drew elements from it.
The exhaust duct design was inspired by the General Dynamics Model 200 design, which was proposed for a 1.972 supersonic VTOL fighter requirement for the Sea Control Ship.

For specialized development of the F-35B STOVL variant, Lockheed consulted with the Yakovlev Design Bureau, purchasing design data from their development of the Yakovlev Yak-141 "Freestyle".
Although several experimental designs have been built and tested since the 1960s including the Navy's unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic, STOVL stealth fighter.

The F-35 has a maximum speed of over Mach 1.6. With a maximum takeoff weight of 60,000 lb (27,000 kg),the Lightning II is considerably heavier than the lightweight fighters it replaces.
In empty and maximum gross weights, it more closely resembles the single-seat, single-engine Republic F-105 Thunderchief, which was the largest single-engine fighter of the Vietnam war era.

However the F-35's modern engine delivers over 60 percent more thrust in an aircraft of the same weight so that in thrust to weight and wing loading it is much closer to a comparably equipped F-16.
Acquisition deputy to the assistant secretary of the Air Force, Lt. Gen. Mark D. "Shack" Shackelford has said that the F-35 is designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition."

Some improvements over current-generation fighter aircraft are:

Durable, low-maintenance stealth technology, using structural fiber mat instead of the high-maintenance coatings of legacy stealth platforms.
Integrated avionics and sensor fusion that combine information from off and on board sensors to increase the pilot's situational awareness and improve target identification and weapon delivery, and to relay information quickly to other command and control (C2) nodes;

High speed data networking including IEEE 1394b[134] and Fibre Channel.
The Autonomic Logistics Global Sustainment (ALGS), Autonomic Logistics Information System (ALIS) and Computerized Maintenance Management System (CMMS) help ensure aircraft uptime with minimal maintenance manpower.

Electrohydrostatic actuators run by a power-by-wire flight-control system.
Lockheed Martin claims the F-35 is intended to have close and long-range air-to-air capability second only to that of the F-22 Raptor.

The company has suggested that the F-35 could also replace the USAF's F-15C/D fighters in the air superiority role and the F-15E Strike Eagle in the ground attack role, but it does not have the range or payload of either F-15 model.
The F-35A does carry a similar air-to-air armament as the conceptual Boeing F-15SE Silent Eagle when both aircraft are configured for low observable operations and has over 80 percent of the larger aircraft's combat radius.

Lockheed Martin has said that the F-35 has the advantage over the F-22 in basing flexibility and "advanced sensors and information fusion".
The majority of the structural composites in the F-35 are made out of bismaleimide (BMI) and composite epoxy material.

However the F-35 will be the first mass produced aircraft to include structural nanocomposites, carbon nanotube reinforced epoxy.

The F-35 program has learned from the corrosion problems that the F-22 had when it was first introduced in 2.005.
The F-35 uses a gap filler that causes less galvanic corrosion to the skin, is designed with fewer gaps in its skin that require gap filler, and has better drainage.

A United States Navy study found that the F-35 will cost 30 to 40 percent more to maintain than current jet fighters.
A Pentagon study found that it may cost $1 trillion to maintain the entire fleet over its lifetime.
Engines

The F-35's main engine is the Pratt & Whitney F135. The General Electric/Rolls-Royce F136 was under development as an alternative engine until December 2.011 when the manufacturers canceled work on it.
The F135/F136 engines are not designed to supercruise in the F-35.
The STOVL versions of both power plants use the Rolls-Royce LiftSystem, patented by Lockheed Martin and developed and built by Rolls-Royce.

This system is more like the Russian Yak-141 and German VJ 101D/E than the preceding generation of STOVL designs,[149] such as the Harrier Jump Jet in which all of the lifting air went through the main fan of the Rolls-Royce Pegasus engine.
The Lift System is composed of a lift fan, drive shaft, two roll posts and a "Three Bearing Swivel Module" (3BSM).
The 3BSM is a thrust vectoring nozzle which allows the main engine exhaust to be deflected downward at the tail of the aircraft.
The lift fan is near the front of the aircraft and provides a counter-balancing thrust using two counter-rotating blisks.

It is powered by the engine's low-pressure (LP) turbine via a drive shaft and gearbox. Roll control during slow flight is achieved by diverting unheated engine bypass air through wing mounted thrust nozzles called Roll Posts.

Like lift engines, the added lift fan machinery increases payload capacity during vertical flight, but is dead weight during horizontal flight.
The cool exhaust of the fan also reduces the amount of hot, high-velocity air that is projected downward during vertical take off, which can damage runways and aircraft carrier decks.
To date, F136 funding has come at the expense of other parts of the program, reducing the number of aircraft built and increasing their costs.

The F136 team has claimed that their engine has a greater temperature margin which may prove critical for VTOL operations in hot, high altitude conditions.
Pratt & Whitney is also testing higher thrust versions of the F135, partly in response to GE's claims that the F136 is capable of producing more thrust than the 43,000 lbf (190 kN) supplied by early F135s.
The F135 has demonstrated a maximum thrust of over 50,000 lbf (220 kN) during testing.

The F-35's Pratt & Whitney F135 is the most powerful engine ever installed in a fighter aircraft.
The F135 is the second (radar) stealthy afterburning jet engine and like the Pratt & Whitney F119 from which it was derived, has suffered from pressure pulsations in the afterburner at low altitude and high speed or "screech". In both cases this problem was fixed during development of the fighter program.
Turbine bearing health in the engine will be monitored with thermoelectric powered wireless sensors.

Armament

The F-35A includes a GAU-22/A, a four-barrel version of the GAU-12 Equalizer 25 mm cannon.
The cannon is mounted internally with 182 rounds for the F-35A or in an external pod with 220 rounds for the F-35B and F-35C.
The gun pod for the B and C variants will have stealth features.

This pod could be used for different equipment in the future, such as electronic warfare equipment, reconnaissance equipment, or possibly a rearward-facing radar.
It has two internal weapons bays, and external hardpoints that can mount four underwing pylons and two near wingtip pylons.
The two outer hardpoints can only carry pylons for the AIM-9X Sidewinder and AIM-132 ASRAAM short range air-to-air missiles.

The other pylons can carry the AIM-120 AMRAAM, Storm Shadow, AGM-158 Joint Air to Surface Stand-off Missile (JASSM) cruise missiles, guided bombs, 480 US gallons (1,800 L) and 600 US gallons (2,300 L) fuel tanks.

The external pylons can carry missiles, bombs and fuel tanks at the expense of being more detectable by radar.

An air-to-air load of eight AIM-120s and two AIM-9s is possible using internal and external weapons stations; a configuration of six 2,000 lb (910 kg) bombs, two AIM-120s and two AIM-9s can also be arranged.
Internally, up to two 2,000 lb (910 kg) air-to-ground bombs can be carried in A and C models (two 1,000 lb (450 kg) bombs in the B model,along with two smaller weapons, normally expected to be air-to-air missiles.
The weapon bays can carry AIM-120 AMRAAM, AIM-132 ASRAAM, the Joint Direct Attack Munition (JDAM) up to 2,000 lb (910 kg), the Joint Stand off Weapon (JSOW), Brimstone anti-armor missiles, and Cluster Munitions (WCMD).[167] With its payload capability, the F-35 can carry more weapons payload than the legacy fighters it is to replace as well as the F-22 Raptor.

Lockheed Martin states that the weapons load can also be configured as all-air-to-ground or all-air-to-air, and has suggested that a Block 5 version will be able to carry three internal weapons per bay instead of two, replacing the heavy bomb with two smaller weapons such as AIM-120 AMRAAM air-to-air missiles.
Upgrades include up to four GBU-39 Small Diameter Bombs (SDB) in each bay (three per bay in F-35B, or four GBU-53/B in each bay for all F-35 variants; The MBDA Meteor air-to-air missile is currently being adapted to fit four internally in the missile spots and may be integrated into the F-35.

A modified Meteor design with smaller tailfins for the F-35 was revealed in September 2.010.
The United Kingdom had originally planned to put up to four AIM-132 ASRAAM internally but this has been changed to carry 2 internal and 2 external ASRAAMs.

The external ASRAAMs are planned to be carried on "stealthy" pylons to increase the F-35's radar cross section slightly; the missile allow attacks to slightly beyond visual range without using radar that might alert the target.
Solid-state lasers were being developed as optional weapons for the F-35 as of 2.002.
The F-35 is expected to take on the Wild Weasel mission, but there are no planned anti-radiation missiles for internal stealthy carrage.
Norway and Australia are funding a program to adapt the Naval Strike Missile (NSM) to fit the internal bays of the F-35.

This will be a multi-role version, named the Joint Strike Missile (JSM), and will be the only cruise missile to fit the internal bays. Studies have shown that the F-35 would be able to carry two of these internally, while four additional missiles could be carried externally. The missile has an expected range in excess of 150 nmi (278 km).

On 12 April 2.011 the Norwegian Ministry of Defense announced phase 2 of development.
The B61 nuclear bomb was scheduled for deployment in 2017, but delays in the F-35 program may delay this.

Stealth and signatures

The F-35 has been designed to have a low radar cross section primarily due to stealthy materials used in construction, including fiber-mat.
Unlike the previous generation of fighters, the F-35 was designed with a shape for low-observable characteristics.

The Teen Series of fighters (F-15, F-16, F/A-18) were notable for always carrying large external fuel tanks, but in order to avoid negating its stealth characteristics the F-35 must fly most missions without external fuel tanks.

Unlike the F-16 and F/A-18, the F-35 lacks leading edge extensions and instead uses stealth-friendly chines for vortex lift in the same fashion as the SR-71 Blackbird.
The small bumps just forward of the engine air intakes form part of the diverterless supersonic inlet (DSI) which is a simpler, lighter means to ensure high-quality airflow to the engine over a wide range of conditions.

These inlets also crucially improve the aircraft's low-observable characteristics.
In spite of being smaller than the F-22, the F-35 has a larger radar cross section. It is said to be roughly equal to a metal golf ball rather than the F-22's metal marble.

The F-22 was designed to be difficult to detect by all types of radars and from all directions.
The F-35 on the other hand manifests its lowest radar signature from the frontal aspect because of compromises in design. Its surfaces are shaped to best defeat radars operating in the X and upper S band, which are typically found in fighters, surface-to-air missiles and their tracking radars, although the aircraft would be easier to detect using other radar frequencies.

Because the shape of the aircraft is so important to its radar cross section, special care must be taken to maintain the "outer mold line" during production.
Ground crews require Repair Verification Radar (RVR) test sets in order to verify the RCS of the aircraft after performing repairs, which was not a concern for previous generations of non-stealth fighters.
Low observable aircraft must consider different types of detection and so the F-35 is not only radar stealthy, but it also has infrared and visual signature reduction incorporated.
In late 2.008 the Air Force revealed that the F-35 would be about twice as loud at takeoff as the McDonnell Douglas F-15 Eagle and up to four times as loud during landing.

As a result, residents near Luke Air Force Base, Arizona and Eglin Air Force Base, Florida, possible home bases for the jet, requested that the Air Force conduct environmental impact studies concerning the F-35's noise levels.
The city of Valparaiso, Florida, adjacent to Eglin AFB, threatened in February 2.009 to sue the Air Force over the impending arrival of the F-35s, but this lawsuit was settled in March 2.010
Moreover, it was reported in March 2009 that testing by Lockheed Martin and the Royal Australian Air Force revealed that the F-35 was not as loud as first reported, being "only about as noisy as an F-16 fitted with a Pratt & Whitney F100-PW-200 engine" and "quieter than the Lockheed Martin F-22 Raptor and the 

Boeing F/A-18E/F Super Hornet."
However according to an acoustics study done by Lockheed Martin and the US Air Force, the noise levels of the F-35 are found to be comparable to the F-22 Raptor and F/A-18E/F Super Hornet.

Cockpit

The F-35 features a full-panel-width "panoramic cockpit display" (PCD) glass cockpit, with dimensions of 20 by 8 inches (50 by 20 centimeters).
A cockpit speech-recognition system (Direct Voice Input) provided by Adacel is planned to improve the pilot's ability to operate the aircraft over the current-generation interface.
The F-35 will be the first US operational fixed-wing aircraft to use this system, although similar systems have been used in AV-8B and trialled in previous US jets, particularly the F-16 VISTA.
A helmet-mounted display system (HMDS) will be fitted to all models of the F-35. A helmet-mounted cueing system is already in service with the F-15s, F-16s and F/A-18s.

While some fighters have offered HMDS along with a head up display (HUD), this will be the first time in several decades that a front line tactical jet fighter has been designed without a HUD.
The F-35 is equipped with a right-hand side stick controller in a standard Lockheed Martin HOTAS configuration.

The Martin-Baker US16E ejection seat is used in all F-35 variants.
The US16E seat design balances major performance requirements, including safe-terrain-clearance limits, pilot-load limits, and pilot size. It uses a twin-catapult system that is housed in side rails.
The General Dynamics F-16 Fighting Falcon has a similar cockpit layout and is being used to train pilots until training F-35s become available.

Sensors and avionics

The F-35's sensor and communications suite is intended to facilitate situational awareness, command-and-control and network-centric warfare capability.
The main sensor on board the F-35 is its AN/APG-81 AESA-radar, designed by Northrop Grumman 
Electronic Systems.

It is augmented by the Electro-Optical Targeting System (EOTS) mounted under the nose of the aircraft, designed by Lockheed Martin.
This gives the same capabilities as the Lockheed Martin Sniper XR while avoiding making the aircraft more easily detectable.

Six additional passive infrared sensors are distributed over the aircraft as part of Northrop Grumman's AN/AAQ-37 distributed aperture system (DAS), which acts as a missile warning system, reports missile launch locations, detects and tracks approaching aircraft spherically around the F-35, and replaces traditional night vision goggles for night operations and navigation.
All DAS functions are performed simultaneously, in every direction, at all times. The F-35's AN/ASQ-239 (Barracuda) Electronic Warfare systems are designed by BAE Systems and include Northrop Grumman components.

The communications, navigation and identification (CNI) suite is designed by Northrop Grumman and includes the Multifunction Advanced Data Link (MADL).
The F-35 will be the first jet fighter that has sensor fusion that combines both radio frequency and IR tracking for continuous target detection and identification in all directions which is shared via MADL to other platforms without compromising low observability.
The F-35 has been designed with synergy between sensors as a specific requirement, with the "senses" of the aircraft expected to provide a more cohesive picture of the reality around it, and be available in principle for use in any possible way, and any possible combination with one another.

All of the sensors feed directly into the main processors to support the entire mission of the aircraft. For example the AN/APG-81 functions not just as a multi-mode radar, but also as part of the aircraft's electronic warfare system.
Unlike previous aircraft, such as the F-22, all software for the F-35 is written in C++ for faster code development.

The Integrity DO-178B real-time operating system (RTOS) from Green Hills Software runs on COTS Freescale PowerPC processors.
The final Block 3 software for the F-35 is planned to have 8.6 million lines of software code.
The scale of the program has led to a software crisis as officials continue to discover that additional software needs to be written.

General Norton Schwartz has said that the software is the biggest factor that might delay the USAF's initial operational capability which is now scheduled for April 2.016.
Michael Gilmore, Director of Operational Test & Evaluation, has written that, "the F-35 mission systems software development and test is tending towards familiar historical patterns of extended development, discovery in flight test, and deferrals to later increments."

The F-35's electronic warfare systems are intended to detect hostile aircraft first, which can then be scanned with the electro-optical system and action taken to engage or evade the opponent before the F-35 is detected.
The CATbird avionics testbed for the F-35 program has proved capable of detecting and jamming F-22 radars.

Helmet-mounted display system

The F-35 does not need to be physically pointing at its target for weapons to be successful.
This is possible because of sensors that can track and target a nearby aircraft from any orientation, provide the information to the pilot through his helmet (and therefore visible no matter which way they are looking), and provide the seeker-head of a missile with sufficient information. Recent missile types provide a much greater ability to pursue a target regardless of the launch orientation, called "High Off-Boresight" capability, although the speed and direction in which the munition is launched affect the effective range of the weapon.

Sensors use combined radio frequency and infra red (SAIRST) to continually track nearby aircraft while the pilot's helmet-mounted display system (HMDS) displays and selects targets.
The helmet system replaces the display suite-mounted head-up display used in earlier fighters.
The F-35's systems provide the edge in the "observe, orient, decide, and act" OODA loop; stealth and advanced sensors aid in observation (while being difficult to observe), automated target tracking helps in orientation, sensor fusion simplifies decision making, and the aircraft's controls allow the pilot to keep their focus on the targets, rather than the controls of their aircraft.

The problems with the current Vision Systems International helmet mounted display led Lockheed Martin to issue a draft specification for proposals for an alternative on 1 March 2.011
The alternative system will be based on Anvis-9 night vision goggles.[221] It will be supplied by BAE systems.
The BAE system does not yet include all the features of the VSI helmet and if successful will have the remaining features incorporated use of the BAE system would also require a cockpit redesign.
In 2.011, Lockheed granted VSI a contract to fix the vibration, jitter, night-vision and sensor display problems in their helmet mounted display.

The improved displays are expected to be delivered in third quarter of 2.013.

Next Generation Jammer

The F-35 was previously considered a platform for the Next Generation Jammer, but attention has shifted to the use of unmanned platforms.

Maintenance

The program's maintenance concept is for any F-35 to be maintained in any F-35 maintenance facility and that all F-35 parts in all bases will be globally tracked and shared as needed.
The aircraft has been designed for ease of maintenance, with 95% of all field replaceable parts "one deep" so that nothing else has to be removed to get to the part in question, the ejection seat can be replaced without removing the canopy, an all-composite skin without the fragile coatings found on other stealth aircraft and low-maintenance electro-hydrostatic actuators instead of hydraulic systems.
Criticisms of the F-35 maintenance concept include the decision to not utilize engine cowling doors.

The decision was instead to use bulkhead mounted airframe panels secured with fasteners across the bottom of the engine bay.
This delays maintenance due to the lengthy removal process of the panels. F-35 maintainers have also noted that the bulkheads block access to several critical engine mounted parts, which means the engine must be removed from the aircraft to access the required parts. 
Such delays in maintenance practices hinder flight test operations.

Operational history
Testing

The first F-35A (designated AA-1) was rolled out in Fort Worth, Texas on 19 February 2.006.
The aircraft underwent extensive ground testing at Naval Air Station Joint Reserve Base Fort Worth in late 2.006.

In September 2.006 the first engine run of the F135 afterburner turbofan in an airframe and tests were completed; the first time that the F-35 was completely functional on its own power systems.
On 15 December 2006, the F-35A completed its maiden flight.
A modified Boeing 737–300, the Lockheed CATBird is used as an avionics test bed inside of which are racks holding all of F-35's avionics, as well as a complete F-35 cockpit.
On 31 January 2.008 at Fort Worth, Texas, Lt Col James "Flipper" Kromberg of the U.S. Air Force became the first military service pilot to evaluate the F-35, taking the aircraft through a series of maneuvers on its 26th flight. F-35 AA-1, on its 34th test flight, began aerial refueling testing in March 2.008.

Another milestone was reached on 13 November 2.008, when the AA-1 flew at supersonic speeds for the first time, reaching Mach 1.05 at 30,000 ft (9,144 m) making four transitions through the sound barrier, for a total of eight minutes of supersonic flight.
The first F-35B (designated BF-1) made its maiden flight on 11 June 2008. The flight, which featured a conventional takeoff, was piloted by BAE Systems' test pilot Graham Tomlinson.
The BF-1 is the second of 19 System Development and Demonstration (SDD) F-35s, and the first to use new weight-optimized design features that will apply to all future F-35s.

Testing of the STOVL propulsion system in flight began on 7 January 2.010.
The STOVL system was used for 14 minutes of the 48 minute test flight while the aircraft slowed from 210 knots (390 km/h) to 180 knots (330 km/h).

The F-35B's first hover (full stop in mid-air) happened on 17 March 2.010, followed by a STOVL landing, and on 18 March 2.010 the first vertical landing was performed.
During a test flight on 10 June 2.010, the F-35B became the second STOVL aircraft to achieve supersonic speeds, the first being its ancestor, the X-35B, which achieved the same feat on 20 July 2.001.
In January 2.011, Lockheed Martin reported it had solved a problem with the aluminum bulkhead used only on the F-35B which had cracked during ground testing.

The first delivered USAF F-35 on its delivery flight to Eglin Air Force Base in July 2.011.
Although many of the initial flight test targets have been accomplished, the F-35 testing program completed "just under 100 sorties and about as many hours in 2.5 years" by June 2.009 and was falling significantly behind schedule.

A 2.008 Pentagon Joint Estimate Team (JET I) estimated that the program was two years behind the latest public schedule, and a 2.009 Joint Estimate Team (JET II) revised that estimate to predict a 30-month delay.
Due to those delays in the testing program, production numbers will be reduced by 122 aircraft through 2.015 in order to provide additional funds for development.
Those additional funds will add $2.8 billion to the development funds and internal memos suggest that the official timeline will be extended by 13 months (not the 30 months the JET II team predicted the slip would be).

The success of the Joint Estimate Team has led Ashton Carter to call for more such teams for other poorly performing Pentagon projects.
In June 2.009, the F-35s APG-81 active electronically scanned array radar was integrated in the Northern Edge 2.009 large-scale military exercise when it was mounted on the front of a Northrop Grumman test aircraft.

The APG-81 test event represented a major milestone in electronic protection testing in an operationally representative environment, accomplished years ahead of normal developmental timelines and providing a significant risk reduction opportunity for the aircraft's key sensor.
The test events "validated years of laboratory testing versus a wide array of threat systems, showcasing the extremely robust electronic warfare capabilities of the world's most advanced fighter fire control radar."

Nearly 30 percent of all the test flights have required more than routine maintenance to get the aircraft flyable again.
As of March 2.010, the F-35 program had used a million more man-hours than predicted and flight testing is expected to result in further design changes.
The United States Navy has projected that lifecycle costs over a fleet life of 65 years for all of the American F-35s will be $442 billion higher than the U.S. Air Force has projected.

The delay in the F-35 program is expected to lead to a shortfall of around 100 jet fighters in the Navy/Marines team. Given careful management, service life extension of the Marines' legacy F/A-18s, and more burdens placed on Navy fighters, it may be possible to reduce this shortfall.
The F-35C carrier variant's maiden flight took place on 7 June 2.010, also at NAS Fort Worth JRB.
The 57 minute flight was executed by Lockheed test pilot Jeff "Slim" Knowles, who was the chief test pilot for the F-117 program.[250] A total of 11 U.S. Air Force F-35s are to arrive in Fiscal Year 2.011.
On 9 March 2.011 all F-35s were grounded after a dual generator failure and oil leak in flight.

This was the first significant flight failure since 2.007.
Seven of the ten test aircraft were cleared to fly four days later.
These aircraft have an older model of generators, unlike the kind that failed in flight.
The problem was found to be the result of faulty maintenance rather than a design or construction issue.
In June 2.011, the F-35's sensors (radar and DAS) were tested in an operational exercise named Northern Edge 2.011.

Navy Cmdr. Erik Etz, the deputy mission systems integrated product team lead from the F-35 JSF Program Office, said the rigorous testing of both sensors during Northern Edge 2.011 served as a significant risk-reduction step for the F-35 JSF program.
"By putting these systems in this operationally rigorous environment, we have demonstrated key war fighting capabilities well in advance of scheduled operational testing," Commander Etz added.

From 3-18 August 2011, the F-35 fleet was grounded. The precautionary grounding was in effect while the Joint Program Office investigated the cause of an electrical system failure on test aircraft, F-35A AF-4 during ground tests.
The Honeywell-built integrated power package (IPP) failed during a standard engine test following a maintenance check on 2 August at Edwards Air Force Base.

The IPP is relatively unheralded, but plays a major role in the F-35's performance. It combines the functions of an environment control unit, engine starter and back-up power generator into a single system.
The IPP has been a target for concern during the development phase, even though it has never failed before in more than 1,500 flight hours.
The JPO was assessing the impact of the grounding on the schedule for the system development and demonstration phase, but the latest version of the schedule included margin for unexpected problems.
On 10 August 2.011, ground operations for the F-35 Program were reinstituted while the investigation was ongoing; government and contractor engineering teams, after reviewing initial data, determined that the fleet could safely resume Development Test ground operations.

Preliminary root cause inquiries indicate that a control valve did not function properly, which in turn led to the IPP failure. Monitoring of this valve is the mitigating action required to allow ground operations.
The F-35 team is revising ground monitoring procedures to ensure testing involving the IPP takes place safely. While initiating DT ground operations is a "major step" for the F-35 fleet returning to flight, further reviews are required prior to lifting the suspension of flight operations for the 20 F-35s currently in flying status.
On 18 August 2.011, the flight ban was lifted for 18 of the 20 fighters.

Two aircraft based at Eglin Air Force Base in Florida will remain grounded because they lack the monitoring systems used in developmental test aircraft that can detect any problems in flight.
On 25 October 2.011 the F-35A reached its designed top speed of Mach 1.6 for the first time.
Further testing demonstrated a speed of Mach 1.61 and 9.9g.
During testing in 2.011, all eight landing tests of the F-35C tail hook failed to catch the arresting wire; the hook design is being modified to address the problem.

Training

In 2.011, the Director of Operational Test and Evaluation warned that the USAF's plans to start unmonitored flight training that fall "risks the occurrence of a serious mishap".
The leaders of the United States Senate Committee on Armed Services have called on Defense Secretary Leon Panetta to address the issue.

The F-35A and F-35B are expected to be cleared for flight training in early 2.012.
And a military flight release was issued on 28 February 2.012.

Procurement and international participation

While the United States is the primary customer and financial backer, the United Kingdom, Italy, the Netherlands, Canada, Turkey, Australia, Norway and Denmark have agreed to contribute US$4.375 billion toward the development costs of the program.
Total development costs are estimated at more than US$40 billion (underwritten largely by the United States), while the purchase of an estimated 2,400 aircraft is expected to cost an additional US$200 billion.

The initial plan was that the nine major partner nations would acquire over 3,100 F-35s through 2.035.
Sales to partner nations are made through the Pentagon's Foreign Military Sales program.
There are three levels of international participation.
The levels generally reflect the financial stake in the program, the amount of technology transfer and subcontracts open for bid by national companies, and the order in which countries can obtain production aircraft.

The United Kingdom is the sole "Level 1" partner, contributing US$2.5 billion, which was about 10% of the planned development costs under the 1995 Memorandum of Understanding that brought the UK into the project.
Level 2 partners are Italy, which is contributing US$1 billion; and the Netherlands, US$800 million. Level 3 partners are Turkey, US$195 million; Canada, US$160 million; Australia, US$144 million; Norway, US$122 million and Denmark, US$110 million. Israel and Singapore have joined as Security Cooperative Participants (SCP).

Japan announced on 20 December 2011 its intent to purchase 42 F-35s with deliveries beginning in 2.016 to replace F-4 Phantom II aircraft. The country wants at least 38 of the F-35s to be assembled in Japan.
By February 2.012 many changes had occurred in the F-35 order book. Italy became the first country to announce it was reducing its overall fleet procurement, cutting its buy from 131 to 90 aircraft. Other nations reduced initial purchases or delayed orders, while still intending to purchase the same final numbers.

The United States canceled the initial purchase of 13 F-35s and postponed orders for another 179. Britain cut its initial order and delayed a decision on future orders.
Australia decided to buy the Boeing Super Hornet as an interim measure until the F-35 is ready.
Turkey also cut its initial order of four aircraft to two, but confirmed plans to purchase 100 F-35As.

The Netherlands and Norway were considering their options and may cut or delay their orders. All of these changes in procurement resulted in increased prices for the aircraft and thus increased the likelihood of further procurement cuts.
Canada does not yet have any intention to reduce its order, claiming an anticipated 75-80$ million unit cost per fighter, and budgeting for cost overruns of ~10%.
Variants

Configuration of the three original F-35 variants

The F-35 is being built in three different main versions to suit various combat missions. A fourth variant, the F-35I is an export version for Israel.

F-35A

The F-35A is the conventional takeoff and landing (CTOL) variant intended for the US Air Force and other air forces. It is the smallest, lightest F-35 version and is the only variant equipped with an internal cannon, the GAU-22/A.
This 25 mm cannon is a development of the GAU-12 carried by the USMC's AV-8B Harrier II. It is designed for increased effectiveness against ground targets compared to the 20 mm M61 Vulcan cannon carried by other USAF fighters.

The F-35A is expected to match the F-16 in maneuverability and instantaneous and sustained high-g performance, and outperform it in stealth, payload, range on internal fuel, avionics, operational effectiveness, supportability, and survivability.
It is expected to match an F-16 that is carrying the usual external fuel tank in acceleration performance.[284] 

It also has an internal laser designator and infrared sensors, equivalent to the Sniper XR pod carried by the F-16, but built in to reduce radar cross section.
The A variant is primarily intended to replace the USAF's F-16 Fighting Falcon. It is also to replace the A-10 Thunderbolt II starting in 2.028.

F-35I

F-35A with Israeli modifications. A senior Israel air force official stated "the aircraft will be designated F-35I, as there will be unique Israeli features installed in them".
The United States will not allow the integration of Israel's own electronic warfare systems into the aircraft’s built-in electronic suite. However, a plug-and-play feature added to the main computer will allow for the use of Israeli electronics in an add-on fashion.

Israel will be able to fit its own external jamming pod and plans to install its own air-to-air missiles and guided bombs in the F-35’s internal weapon bays.
In July 2.011, it was reported that the U.S. had agreed to allow Israel to install their own electronic warfare systems and missiles in their F-35s in the future.
Israel Aerospace Industries has considered playing a role in the development of a proposed two-seat F-35. An IAI executive stated, "There is a known demand for two seats not only from Israel but from other air forces.

Advanced aircraft are usually two seats rather than single seats."[289] IAI also plans to produce conformal fuel tanks to extend the range.
CF-35
The Canadian CF-35 will differ from the American F-35A through the addition of a drag chute and an F-35B/C style refueling probe.

Norway may also use the drag chute option, as they also have icy runways.

F-35B

The Pratt & Whitney F135 engine with lift fan, roll posts, and rear vectoring nozzle, as designed for the F-35B, at the Paris Air Show, 2.007.
F-35B vertical landing during its first sea trials aboard USS Wasp (LHD-1), October 2.011.
F-35B short-takeoff from USS Wasp (LHD-1) during its first sea trials, October 2.011.
The F-35B is the short takeoff and vertical landing (STOVL) variant of the aircraft.

Similar in size to the A variant, the B sacrifices about a third of the other version's fuel volume to make room for the vertical flight system.
Takeoffs and landing with vertical flight systems are by far the riskiest, and in the end, a decisive factor in design.

Like the AV-8B Harrier II, the B’s guns will be carried in a ventral pod. Whereas the F-35A is stressed to 9 g, the F-35B is stressed to 7 g.
The F-35B was unveiled at Lockheed Martin's Fort Worth plant on 18 December 2.007, and the first test flight was on 11 June 2.008.
Unlike the other variants, because it can land vertically the F-35B has no landing hook.

The "STOVL/HOOK" button in the cockpit initiates conversion instead of dropping the hook.
The F-35B sends jet thrust directly downwards during vertical takeoffs and landing and the nozzle is being redesigned to spread the output out in an oval rather than a small circle so as to limit damage to asphalt and ship decks.
The variant's three-bearing swivel nozzle that directs the full thrust of the afterburning jet engine is moved by a “fueldraulic” actuator, using pressurized jet fuel.

The United States Marine Corps plans to purchase 340 F-35Bs,[84] to replace all current inventories of the F/A-18 Hornet (A, B, C and D-models), and AV-8B Harrier II in the fighter, and attack roles.
The Marines are planning to use the F-35B from "unimproved surfaces at austere bases" and are preparing landing spots with "special, high-temperature concrete designed to handle the heat from the JSF".

The Royal Air Force and Royal Navy had plans to use the F-35B to replace their Harrier GR9s. One of the Royal Navy requirements for the F-35B design was a Shipborne Rolling and Vertical Landing (SRVL) mode to increase the maximum landing weights for carried weapons via wing lift.
This method of landing is slower than arrested landing and could disrupt regular carrier operations.

However, in October 2.010, the UK announced plans to order to the CATOBAR F-35C variant instead.
In March 2012 sources at the UK Ministry of Defence were quoted as saying that the UK was reconsidering, and might buy the F-35B instead, because of the cost of equipping the UK's new aircraft carriers for the F-35C.
Italian Navy is preparing Grottaglie air station for future operations with the F-35B. The Italian Navy is to receive 22 aircraft between 2.014 and 2.021, with its Cavour aircraft carrier set to be modified to operate them by 2.016.

Commandant of the Marine Corps, General James Amos has said that, in spite of its increasing costs and schedule delays, there is no plan B to substitute for the F-35B.
The F-35B is larger than the aircraft it replaces, which required the USS America (LHA-6) to be designed without needed well deck capabilities.
In 2.011, the USMC and USN signed an agreement that the USMC will purchase 340 F-35B and 80 F-35C while the USN will purchase 260 F-35C.
The five squadrons of Marine Corps F-35Cs will be assigned to the Navy carriers while the Marine Corps F-35Bs will be used on Amphibious ships and ashore.

On 6 January 2.011, Gates said that the 2.012 budget would call for a two year pause in F-35B production during which the aircraft may be redesigned, or canceled if unsuccessful.
Gates stated, "If we cannot fix this variant during this time frame, and get it back on track in terms of performance, cost and schedule, then I believe it should be canceled."

The probation was ended by Defense Secretary Leon Panetta on 20 January 2012 because of progress made over the past year.
Lockheed Martin executive vice president Tom Burbage and former Pentagon director of operational testing 

Tom Christie have said that most of the delays in the total program have been due to issues with the F-35B, which forced massive redesigns on the other versions.
The USMC intends to declare Initial Operational Capability with about 50 F-35s running interim Block 2B software in the 2.014 to 2.015 timeframe.
Lockheed Martin vice president Steve O’Bryan has said that most F-35B landings will be purely conventional in order to reduce stress on the vertical lift components.

Conventional operations also reduce the risk of self-induced foreign object damage.
On 3 October 2.011, the F-35B began its initial sea-trials by performing a vertical landing on the deck of the amphibious assault ship USS Wasp.

F-35C

F-35C launching from an electromagnetic catapult during testing, November 2.011.
Compared to the F-35A, the F-35C carrier variant features larger wings with foldable wingtip sections, larger wing and tail control surfaces for improved low-speed control, stronger landing gear for the stresses of carrier arrested landings, a twin-wheel nose gear, and a stronger tailhook for use with carrier arrestor cables.

The larger wing area allows for decreased landing speed while increasing both range and payload. With twice the range on internal fuel as the F/A-18C Hornet, the F-35C achieves much the same goal as the F/A-18E/F Super Hornet.
The United States Navy will use the F-35C carrier variant. It intends to buy 480 F-35Cs to replace the F/A-18A, B, C, and D Hornets.
The F-35C will also serve as a low-observable complement to the Super Hornet.[323] On 27 June 2.007, the carrier variant completed its Air System Critical Design Review (CDR).

This allows the first two functional prototype F-35C units to be produced.
The C variant is expected to be available beginning in 2.014.
The first F-35C was rolled out on 29 July 2.009.

On 6 November 2010, the first F-35C arrived at Naval Air Station Patuxent River, however, it was determined that the replacement engines for at-sea repair are too large to be transported by current underway replenishment systems.
The United States Marine Corps will also purchase 80 F-35Cs, enough for five Marine fighter-attack squadrons, for use with Navy carrier air wings in a joint service agreement signed on 14 March 2.011.
In October 2.010, the United Kingdom decided to order the F-35C, which will be used by both the Royal Air Force and the Royal Navy.

The total number of F-35C aircraft to be procured will not be decided until the 2015 Strategic Defence Review.
However, it will be less than the 138 originally ordered; reports have suggested a fleet of around 50.
The Royal Navy's new Queen Elizabeth class aircraft carriers are large enough to support non-STOVL operations and as a result, at least one carrier will have catapults and arrestor cables installed to allow F-35C operations.

The carrier will typically carry 12 F-35Cs with the ability to deploy up to 36.
The UK Strategic Defence & Security Review found that the F-35C's greater endurance in the air meant that fewer aircraft would be needed and that the F-35C has a 25 percent lower lifetime cost than the F-35B.
In 2.011 the F-35Cs were grounded for six days because of a software error in the code that was intended to keep the wings from folding in mid-flight.

But on 27 July 2.011, the F-35C test aircraft CF-3 completed its first steam catapult launch during a test flight in Naval Air Engineering Station Lakehurst.
The TC-13 Mod 2 test steam catapult, representative of current fleet technology, was used. In addition to the catapult launches at varying power levels, the integrated test team is to execute a test plan over three weeks to include dual-aircraft jet blast deflector testing and catapult launches using a degraded catapult configuration to measure the effects of steam ingestion on the aircraft.

On 13 August 2.011, the F-35 integrated test force completed jet blast deflector (JBD) testing at the Lakehurst facility, with a round of two-aircraft testing. F-35C test aircraft CF-1 along with an F/A-18E tested a combined JBD cooling panel configuration to assess the integration of F-35s in aircraft carrier launch operations.

“We completed all of our JBD test points efficiently,” said Andrew Maack, government chief test engineer. “It was a great collaborative effort by all parties.”
The government and industry team completed tests that measured temperatures, pressures, sound levels, velocities, and other environmental data.
The combined JBD model is to enable carrier deck crews to operate all air wing aircraft, now including the F-35C, as operational tempo requires.

Future carrier suitability testing is scheduled throughout 2.011, including ongoing catapult testing and the start of arrestment testing in preparation for initial ship trials in 2.013.
On 18 Nov 2.011, the US Navy used its new Electromagnetic Aircraft Launch System (EMALS) to catapult an F-35C into the air for the first time.

Specifications (F-35A)
General characteristics :

Crew: 1
Length: 51.4 ft (15.67 m)
Wingspan: 35 ft[N 5] (10.7 m)
Height: 14.2 ft[N 6] (4.33 m)
Wing area: 460 ft²[167] (42.7 m²)
Empty weight: 29,300 lb (13,300 kg)
Loaded weight: 49,540 lb[128][N 7](22,470 kg)
Max. takeoff weight: 70,000 lb[N 8] (31,800 kg)
Powerplant: 1 × Pratt & Whitney F135 afterburning turbofan
Dry thrust: 28,000 lbf[339][N 9] (125 kN)
Thrust with afterburner: 43,000 lbf
Internal fuel capacity: 18,480 lb (8,382 kg)

Performance

Maximum speed: Mach 1.6+[162] (1,200 mph, 1,930 km/h) (Tested to Mach 1.61)
Range: 1,200 nmi (2,220 km) on internal fuel
Combat radius: 584 nmi(1,080 km) on internal fuel
Service ceiling: 60,000 ft[344] (18,288 m) (Tested to 43,000 ft)
Rate of climb: classified (not publicly available)
Wing loading: 91.4 lb/ft² (446 kg/m²)
Thrust/weight:
With full fuel: 0.87
With 50% fuel: 1.07
g-Limits: 9 g[N 11]

Armament

Guns: 1 × General Dynamics GAU-22/A Equalizer 25 mm (0.984 in) 4-barreled gatling cannon, internally mounted with 180 rounds.
Hardpoints: 6 × external pylons on wings with a capacity of 15,000 lb (6,800 kg) and 2 internal bays with 2 pylons each for a total weapons payload of 18,000 lb (8,100 kg)and provisions to carry combinations of:
Missiles:
Air-to-air missiles:
AIM-120 AMRAAM
AIM-9X Sidewinder
IRIS-T
MBDA Meteor (Pending further funding)
JDRADM (after 2020)
Air-to-surface missiles:
AGM-154 JSOW
AGM-158 JASSM
Brimstone missile
Joint Air-to-Ground Missile
Storm Shadow missile
SOM

Anti-ship missiles:

JSM
Bombs:
Mark 84, Mark 83 and Mark 82 GP bombs
Mk.20 Rockeye II cluster bomb
Wind Corrected Munitions Dispenser capable
Paveway-series laser-guided bombs
Small Diameter Bomb (SDB)
JDAM-series
B61 nuclear bomb


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